In the field of display technology, organic light-emitting diodes (OLED) have been widely used. In display panels, driving transistors can generate a driving current according to a data voltage, so as to drive the OLED to emit light for displaying. Threshold voltages of the driving transistors may affect the correspondence between the data voltage and the driving current. Different driving transistors may have different threshold voltages. Further, the threshold voltage of the same driving transistor may be varied over time. Therefore, it is not always to obtain the same driving current with respect to the same data voltage, which may cause the display panel to emit light non-uniformly.